Semantic segmentation on multi-resolution optical and microwave data using deep learning

Presently, deep learning and convolutional neural networks (CNNs) are widely used in the fields of image processing, image classification, object identification and many more. In this work, we implemented convolutional neural network based modified U-Net model and VGG-UNet model to automatically identify objects from satellite imagery captured using high resolution Indian remote sensing satellites and then to pixel wise classify satellite data into various classes. In this paper, Cartosat 2S (~1m spatial resolution) datasets were used and deep learning models were implemented to detect building shapes and ships from the test datasets with an accuracy of more than 95%. In another experiment, microwave data (varied resolution) from RISAT-1 was taken as an input and ships and trees were detected with an accuracy of >96% from these datasets. For the classification of images into multiple-classes, deep learning model was trained on multispectral Cartosat images. Model generated results were then tested using ground truth. Multi-label classification results were obtained with an accuracy (IoU) of better than 95%. Total six different problems were attempted using deep learning models and IoU accuracies in the range of 85% to 98% were achieved depending on the degree of complexity.

Population estimation using 3D city modelling and Carto2S datasets -- A case study

With the launch of Carto2S series of satellites, high resolution images (0.6-1.0 meters) are acquired and available for use. High resolution Digital Elevation Model (DEM) with better accuracies can be generated using C2S multi-view and multi date datasets. DEMs are further used as an input to derive Digital terrain models (DTMs) and to extract accurate heights of the objects (building and tree) over the surface of the Earth. Extracted building heights are validated with ground control points and can be used for generation of city modelling and resource estimation like population estimation, health planning, water and transport resource estimations. In this study, an attempt is made to assess the population of a township using high-resolution Indian remote sensing satellite datasets. We used Carto 2S multi-view data and generated a precise DEM and DTM over a city area. Using DEM and DTM datasets, accurate heights of the buildings are extracted which are further validated with ground data. Accurate building heights and high resolution imagery are used for generating accurate virtual 3D city model and assessing the number of floor and carpet area of the houses/ flats/ apartments. Population estimation of the area is made using derived information of no of houses/ flats/ apartments from the satellite datasets. Further, information about number of hospital and schools around the residential area is extracted from open street maps (OSM). Population estimation using satellite data and derived information from OSM datasets can prove to be very good tool for local administrator and decision makers.

Tree level change detection over Ahmedabad city using very high resolution satellite images and Deep Learning

In this study, 0.5m high resolution satellite datasets over Indian urban region was used to demonstrate the applicability of deep learning models over Ahmedabad, India. Here, YOLOv7 instance segmentation model was trained on well curated trees canopy dataset (6500 images) in order to carry out the change detection. During training, evaluation metrics such as bounding box regression and mask regression loss, mean average precision (mAP) and stochastic gradient descent algorithm were used for evaluating and optimizing the performance of model. After the 500 epochs, the mAP of 0.715 and 0.699 for individual tree detection and tree canopy mask segmentation were obtained. However, by further tuning hyper parameters of the model, maximum accuracy of 80 % of trees detection with false segmentation rate of 2% on data was obtained.